In urban development, the rational utilization of water resources and water quality assurance have always been important issues. With the acceleration of industrial development and urbanization, the requirements for water treatment technology are increasing. Submerged ultrafiltration technology, as an advanced water treatment technology, plays an important role in municipal water treatment and industrial wastewater recycling. It can not only effectively improve water quality but also achieve efficient recycling of water resources, providing strong support for sustainable urban development.

Principle of Submerged Ultrafiltration Technology

Ultrafiltration is a process based on physical separation, using low pressure to drive the separation and filtration of fluids according to the molecular weight of the solute. Its pore size is approximately 0.002 to 0.1 microns. In the ultrafiltration process, dissolved substances and substances smaller than the membrane pore size pass through the membrane to form permeate, while substances that cannot pass through the filter membrane are concentrated in the effluent and discharged through concentrate discharge, and those remaining on the membrane are removed by backwashing or chemical cleaning.

The submerged ultrafiltration membrane is immersed in the water tank to be treated. The water intake channel is completely open, and the water is sucked in from the outside under negative pressure, using the pressure difference as the driving force to physically separate the liquid using the membrane pores. This technology has unique advantages, such as excellent membrane fiber material, advanced preparation technology, and the use of excellent PVDF high-polymer material to prepare membrane fibers with a support layer. The support layer is firmly bonded to the PVDF membrane layer, resulting in high membrane fiber strength and effectively avoiding membrane fiber breakage. At the same time, its pore size distribution is narrow, the filtration precision is high, the average pore size is <0.1μm, and it can effectively remove suspended solids, bacteria, protozoa, and colloids, with a water turbidity of less than 0.1NTU.

Characteristics of Submerged Ultrafiltration Technology

High Efficiency: Submerged ultrafiltration technology can effectively remove harmful substances such as suspended solids, colloids, and bacteria in water. The water quality meets the national "Hygiene Standard for Drinking Water" (GB5749-2022), and the effluent water quality is stably below 0.1NTU, with strong resistance to shock loads.

Energy Saving: The technology can reduce the addition of flocculants and disinfectants, reduce the generation of disinfection byproducts, increase the amount of water treated per unit area, and save land. At the same time, it realizes modern, automated, and intelligent control, reducing energy consumption and operating costs.

Stability: The membrane fiber material is excellent, with good chemical stability, corrosion resistance, acid and alkali resistance, and oxidation resistance. High-efficiency chemical cleaning agents can be used to clean the membrane modules. It has good hydrophilicity, stronger anti-pollution ability, permanent hydrophilicity, and significant performance recovery after pollution.

Strong Adaptability: The submerged ultrafiltration membrane module is directly immersed in water, and water is produced by negative pressure suction. It has strong shock resistance to high-concentration suspended solids, high-concentration organic matter, and unstable water quality.

Application of Submerged Ultrafiltration Technology

Lisheng Enterprise has extensive applications in the field of municipal water treatment, realizing modern, automated, and intelligent control for new water plants and modular construction for the upgrading and transformation of old water plants. As of 2023, the application scale of Lisheng ultrafiltration membranes in ultrafiltration membrane water plants nationwide has exceeded 4.5 million tons/day, ranking among the industry leaders. Lisheng ultrafiltration membrane solutions have become the core technology of the "third-generation water treatment process," working with dozens of cities in China and overseas cities to improve urban water quality and improve drinking water taste.

Taking the Haikou Jiangdong high-quality drinking water plant as an example, this plant uses advanced technology of "pre-ozonation, enhanced conventional treatment, ozone activated carbon, and ultrafiltration membrane deep treatment," achieving internationally leading water quality. After the project was completed, it produces 300,000 m³ of high-quality water every day, greatly improving the drinking water quality in the Jiangdong New District. The Nantong Langshan Water Plant uses a combined process of ozone activated carbon + ultrafiltration membrane technology to effectively reduce organic matter and ensure drinking water safety.

The ultrafiltration effluent is about 0.05 NTU, and the sand filtration effluent is 0.2-0.3 NTU. The number of particles in the ultrafiltration effluent is significantly more stable than that of the sand filtration membrane system, improving the problems of high organic matter, turbidity, and microbial content in the effluent of traditional processes. The Langfang surface water plant uses submerged ultrafiltration membrane technology to produce 300,000 m³ of high-quality drinking water per day, fully meeting the water demand of Langfang's main urban area and providing solid support for the water supply of the air economic zone and the Wan Zhuang area.

Hangzhou Xinsheng Dyeing Co., Ltd. in Dangwan Town uses submerged ultrafiltration technology to establish intelligent water control. The company's wastewater enters the factory's wastewater reuse facility, and after passing through membrane bioreactor and reverse osmosis treatment systems, high-quality recycled water is used for production. The factory's wastewater reuse facility uses an internationally advanced dyeing wastewater membrane treatment system, combined with the characteristics of wastewater quality for treatment, to improve the amount of recycled water and the reuse rate.

The company has also established intelligent water control, with real-time alarm and water use analysis functions, monitoring the water consumption of various processes in the workshop. Through new technologies, the company's wastewater reuse rate has increased to 38%, the water reuse rate has increased by 12%, and the water consumption per unit product has decreased by 35%.